China Construction Bank Corp said it has approached more than 50 companies that could convert debt to equity as part of the nation's efforts to tame an explosion in corporate leverage that poses risks for financial stability.

The bank assessed the firms' debt levels, industry indicators, and the strength of their relationships with CCB, said Zhang Minghe, who is leading the bank's swap program, called "Spring Rain." The companies include State-owned enterprises and private firms in industries from steel to coal, Zhang said at a briefing in Beijing on Tuesday.

The banker was commenting after CCB in the past week announced deals with Wuhan Iron Steel Group and Yunnan Tin Group worth more than 34 billion yuan ($5 billion) and aimed at cutting leverage. Zhang said that the approach laid out by the government for the debt-to-equity initiative had avoided what bankers would be "most scared of" - deals where the State was matchmaker.

Zhang said it was difficult to forecast how big the program would get, because it is market-oriented, rather than being subject to a government quota.

In the Yunnan Tin deal, a CCB unit is raising money from investors to buy 10 billion yuan of loans extended by other lenders, according to the bank. None of the debt is non-performing.

The unit gets stakes in Yunnan Tin subsidiaries, with the expectation of eventually being bought out. The investors, which include insurers, pension funds, and private-banking clients, may get returns of between 5 and 15 percent annually over five years, without any guarantees, according to the bank.

Debt-to-equity swaps involving companies abroad that have borrowed from Chinese lenders are also possible, according to Zhang.

CCB, which is China's second-biggest lender, plans to set up a specialized "execution agency" for debt-to-equity swaps, Zhang said. Banks can't convert debt into equity directly, and instead must work through such execution agencies.

Chinese policy makers are stepping up their fight against excessive leverage, with the cabinet last week releasing guidelines for reducing corporate debt and swapping debt for equity.